This invention relates to winches and more particularly to geared sailboat winches having a feature to enable reverse action of the normal cranking movement under certain conditions.
Conventional sailboat winches, such as those described in U.S. Pat. No. 4,261,549 and references cited therein, incorporated herein by reference, comprise a rotary line receiving drum mounted on a fixed support base secured to the deck of a sailboat or other support structure. The drum is rotated in one direction by cranking a central shaft connected by gears to the drum A line, connected to a sail or other operative elements of a sailboat, is wrapped around the drum in frictional engagement therewith. A reduced gear ratio is typically provided between the central shaft and the drum to provide a mechanical advantage and reduce the effort required to crank in the line under tension.
As will be described in more detail herein in connection with FIG. 2, it is well known to provide a winch with more than one speed. Multiple speed winches have drums which are capable of rotation in only one direction, usually a clockwise direction. Rotation in a counterclockwise direction is prevented by a ratchet mechanism, which usually comprises spring loaded pawls engageable in detents in the gear drive, or some equivalent mechanism. An extra speed is attained by the use of an extra gear which becomes operable upon reversal of rotary motion of the main drive shaft. For example, a typical two speed winch will have a 1:1 ratio when the drive shaft is rotated in a clockwise direction and a lower drive ratio when the drive shaft is cranked or rotated in a counterclockwise direction, with the drum always moving in a clockwise direction. When trimming in a sheet for a sail, the line initially has low tension, and a high cranking ratio is desired. When the sail is almost completely trimmed, the tension on the sheet or line increases substantially, and a lower cranking ratio is desired. The cranking power to the input drive shaft of the winch may be provided by a manual crank or an electrical or hydraulic motor.
Sailboat winches are produced in a variety of sizes or drum diameters and a variety of speeds and gear ratios to accommodate sailboats of various sizes. As the sail area and weight of a yacht increases, the sheeting loads exerted on the winch increase very substantially. In fact, the load on the line at the winch of a large sailboat may be so high when the sail is fully trimmed that it may be dangerous for an individual to release or ease out the line by hand, and controlled release of the tension may be very difficult.
In view of the above considerations, it is desirable to provide a high load capacity winch with a so-called backwind feature. It is known to connect the drive of a winch to a worm gear which can be operated to rotate the winch drum in a counterclockwise direction or opposite to the winding direction and relieve the initial high pressure or tension on the line to a safe level. The worm gear remains locked during normal operation of the winch. Previous proposals for backwind winches, however, have required a mechanism to deactivate at least one set of the one-way ratchet mechanisms in the gear chain to allow reverse movement of the drum. These proposals have been very complicated and costly, and the winch is limited to one winding drive speed when the backwind mechanism is employed.
In view of the foregoing, it would be desirable to provide a sailboat winch with a backwind feature which may be operated independently of the one-way ratchet or pawl mechanisms commonly employed in winches of this nature, while leaving the main drive train fully connected and operational.